Cu-rich amalgam microstructures and alterations in microstructures resulting from corrosion will be studied. The identification of corrosion products and corresponding microstructural changes as a function of immersion time in four physiologically related solutions will be conducted by scanning electron microscopy and x-ray analyses. These findings will assist in determining the nature and rate of potential degradation of various Cu-rich amalgam systems. The compositions and lattice parameters of phases in different brands of Cu-rich amalgams will be compared with those of the corresponding stoichiometric phases. These investigations are intended to identify deviations from stoichiometric phase relationships which could have major influences on the performance of amalgam restorations. The effect of age of amalgam alloys on the phase contents of amalgams will be studied. Changes in phase contents can have major effects on clinical handling and restoration longevity. These investigations will assist in the development of methods to overcome the source of deleterious effects on clinical performance.